diff --git a/behat/symfony2-extension/2.1/features/bootstrap/bootstrap.php b/behat/symfony2-extension/2.1/features/bootstrap/bootstrap.php
index f215631d..3dd50381 100644
--- a/behat/symfony2-extension/2.1/features/bootstrap/bootstrap.php
+++ b/behat/symfony2-extension/2.1/features/bootstrap/bootstrap.php
@@ -4,5 +4,8 @@ use Symfony\Component\Dotenv\Dotenv;
 
 // The check is to ensure we don't use .env in production
 if (!isset($_SERVER['APP_ENV'])) {
+    if (!class_exists(Dotenv::class)) {
+        throw new \RuntimeException('APP_ENV environment variable is not defined. You need to define environment variables for configuration or add "symfony/dotenv" as a Composer dependency to load variables from a .env file.');
+    }
     (new Dotenv())->load(__DIR__.'/../../.env');
 }
diff --git a/symfony/console/3.3/bin/console b/symfony/console/3.3/bin/console
index 9f0dd4ea..d026a6d2 100755
--- a/symfony/console/3.3/bin/console
+++ b/symfony/console/3.3/bin/console
@@ -16,6 +16,9 @@ if (!class_exists(Application::class)) {
 }
 
 if (!isset($_SERVER['APP_ENV'])) {
+    if (!class_exists(Dotenv::class)) {
+        throw new \RuntimeException('APP_ENV environment variable is not defined. You need to define environment variables for configuration or add "symfony/dotenv" as a Composer dependency to load variables from a .env file.');
+    }
     (new Dotenv())->load(__DIR__.'/../.env');
 }
 
diff --git a/symfony/framework-bundle/3.3/public/index.php b/symfony/framework-bundle/3.3/public/index.php
index d5255812..3c7ed08f 100644
--- a/symfony/framework-bundle/3.3/public/index.php
+++ b/symfony/framework-bundle/3.3/public/index.php
@@ -9,6 +9,9 @@ require __DIR__.'/../vendor/autoload.php';
 
 // The check is to ensure we don't use .env in production
 if (!isset($_SERVER['APP_ENV'])) {
+    if (!class_exists(Dotenv::class)) {
+        throw new \RuntimeException('APP_ENV environment variable is not defined. You need to define environment variables for configuration or add "symfony/dotenv" as a Composer dependency to load variables from a .env file.');
+    }
     (new Dotenv())->load(__DIR__.'/../.env');
 }